Cloth colliding through mesh?
Ok, I just did a simpler rig now the answer is which is not very certain that I could only figure out there must be something wrong with how you adjusted the armature and the pinned vertices most probably won't move so the leg that's kicking is something you need to unpin like:



make sure you enable the cloth simulation on the physics tab ONLY FOR THE CLOTH(PANTS) and the collision set only for the mesh. and hence the result:

(this is a simpler rig though.)